95 research outputs found
Special scrolls whose base curve has general moduli
In this paper we study the Hilbert scheme of smooth, linearly normal, special
scrolls under suitable assumptions on degree, genus and speciality.Comment: Latex2e, shorter versio
On the geometric genus of reducible surfaces and degenerations of surfaces to unions of planes
In this paper we study some properties of degenerations of surfaces whose
general fibre is a smooth projective surface and whose central fibre is a
reduced, connected surface , , which is assumed to be
a union of smooth projective surfaces, in particular of planes. Our original
motivation has been a series of papers of G. Zappa which appeared in the
1940-50's regarding degenerations of scrolls to unions of planes.
Here, we present a first set of results on the subject; other aspects are
still work in progress and will appear later.
We first study the geometry and the combinatorics of a surface like ,
considered as a reduced, connected surface on its own; then we focus on the
case in which X is the central fibre of a degeneration of relative dimension
two over the complex unit disk. In this case, we deduce some of the intrinsic
and extrinsic invariants of the general fibre from the ones of its central
fibre.
In the particular case of a central fibre of a semistable degeneration,
i.e. has only global normal crossing singularities and the total space of
the degeneration is smooth, some of the above invariants can be also computed
by topological methods (i.e., the Clemens-Schmid exact sequence). Our results
are more general, not only because the computations are independent on the fact
that is the central fibre of a degeneration, but also because the
degeneration is not semistable in general.Comment: latex2e, 26 pages, 11 figure
On the first Gaussian map for Prym-canonical line bundles
We prove by degeneration to Prym-canonical binary curves that the first
Gaussian map of the Prym canonical line bundle is
surjective for the general point [C,A] of R_g if g >11, while it is injective
if g < 12.Comment: To appear in Geometriae Dedicata. arXiv admin note: text overlap with
arXiv:1105.447
Equivalent birational embeddings II: divisors
Two divisors in are said to be Cremona equivalent if there is a
Cremona modification sending one to the other. We produce infinitely many non
equivalent divisorial embeddings of any variety of dimension at most 14. Then
we study the special case of plane curves and rational hypersurfaces. For the
latter we characterise surfaces Cremona equivalent to a plane.Comment: v2 Exposition improved, thanks to referee, unconditional
characterization of surfaces Cremona equivalent to a plan
Neonatal heart failure and noncompaction/dilated cardiomyopathy from mucopolysaccharidosis. First description in literature
Mucopolysaccharidosis are genetic disorders due to deficiency of lysosomal enzymes, resulting in abnormal glycosaminoglycans accumulation in several tissues. Heart involvement tends to be progressive and worsens with age. We describe the first case of mucopolysaccharidosis type I presenting with noncompaction/dilated-mixed cardiomyopathy and heart failure within neonatal period, which responded successfully to specific metabolic treatment. Cardiac function recovered after enzyme replacement therapy and hematopoietic stem cell transplantation, adding to the existing knowledge of the disease
Interacting Preformed Cooper Pairs in Resonant Fermi Gases
We consider the normal phase of a strongly interacting Fermi gas, which can
have either an equal or an unequal number of atoms in its two accessible spin
states. Due to the unitarity-limited attractive interaction between particles
with different spin, noncondensed Cooper pairs are formed. The starting point
in treating preformed pairs is the Nozi\`{e}res-Schmitt-Rink (NSR) theory,
which approximates the pairs as being noninteracting. Here, we consider the
effects of the interactions between the Cooper pairs in a Wilsonian
renormalization-group scheme. Starting from the exact bosonic action for the
pairs, we calculate the Cooper-pair self-energy by combining the NSR formalism
with the Wilsonian approach. We compare our findings with the recent
experiments by Harikoshi {\it et al.} [Science {\bf 327}, 442 (2010)] and
Nascimb\`{e}ne {\it et al.} [Nature {\bf 463}, 1057 (2010)], and find very good
agreement. We also make predictions for the population-imbalanced case, that
can be tested in experiments.Comment: 10 pages, 6 figures, accepted version for PRA, discussion of the
imbalanced Fermi gas added, new figure and references adde
EFFECT OF N2 PARTIAL PRESSURE ON THE GROWTH OF CHROMIUM NITRIDE COATINGS
Chromium nitride films has been prepared by reactive magnetron sputtering using a mixture of Ar and N2 gas. Keeping constant the total pressure during the film deposition the ratio of N2 to Ar has been varied from 0.3 to 5.0 to promote the growth of CrN films with different microstructure. The structural chemical characterization of grown films were performed by means of x-ray diffraction and scanning electron microscopy, auger electron spectroscopy and x-ray photoemission spectroscopy. Even if no clear correlation between material hardness and coating microstructure was observed with nanoindentation, the tribological characterization of the films, evidenced a strong dependence of the wear rate of the material by the process conditions. In particular we observed an improved wear resistance for coatings with a compressive residual stress
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